Ball mills



A. R. BRYAN BALL MILLS March 16, 1965 4 Sheets-Sheet 1 Filed April 12 1965 RM N mm M

mam

.AMM

w\ 3 5 mm NM QQ NM .w.- T N N A TTOEA/EY March 16, 1965 A. R. BRYAN 3,173,619

BALL MILLS Filed April 12, 1965 4 Sheets-Sheet 2 mvsmon AL/F R. 5/? YA/v flow/lea 0. OER/AM Arroeusy A. R. BRYAN BALL MILLS March 16, 1965 4 Sheets-Sheet 3 Filed April 12, 1963 &

INVENTOR. AL/F' R. BRYAN BY 1522144420 0. OER/AN March 16, 1965 A. R. BRYAN 3,173,619

BALL MILLS Filed April 12, 1965 4 Sheets-Sheet 4 FIG. 7 204 FIG.

INVENTOR. AL/F A. 5e mu [QM/A20 0. 032mm A TTQQA/Ey Fatented Mar. 16, 1965 3,173,619 BALL MILLS Alif R. Bryan, Tehachapi, Califl, assignor to Monolith Portland Cement (10., Los Angeles, Calif., a corporation of Nevada Filed Apr. 12, 1963, Ser. No. 272,694 13 Claims. ((11. 241-153) This invention pertains to new and improved ball mills and to methods utilizing the same.

The term ball mill is commonly employed to designate a grinding mill which includes a shell having an axis, means for rotating this shell about its axis and a charge of material located within the shell. Such a charge of material normally consists of a plurality of particles serving to facilitate grinding as well as a charge of material to beg round. Commonly balls, pebbles, rods or the like are utilized as the grinding media in a mill of this type. The shell in a mill of this type is normally of a cylindrical configuration, however, various conically shaped shells and shells of other configurations are used in grinding mills falling within the broad classification of ball mills. Frequently such mills are referred to by other terms such as rod mills, tube mills, compartment mills and the like, depending upon the manners in which they are designed and the material used as a grinding media in them.

When a ball mill is operated the material being ground as Well as the particles of the grinding media generally abrade against one another so as to accomplish a certain amount of grinding. Normally a ball mill is operated so that such abrasion while important in grinding is secondary to the grinding achieved by cascading the particles used as grinding media and some of the charge across the interior of the ball mill by operating it so that its shell is rotated at such speed as to impart sufficient movement to the contents of the shell so as to cause these contents to be lifted and thrown or dropped down against the bottom portion of the shell so as to hit against the shell and any material already accumulated in this bottom portion.

Mills of the general category indicated in the preceding are probably employed for the vast majority of industrial grinding operations. It is well known that conventional ball mills are comparatively inelficient in virtually every imaginary sense of the term efiiciency. Thus, for example, the power consumption in grinding with a ball mill is normally exceedingly high. Further, a conventional ball mill is a comparatively slow piece of equipment to utilize in grinding any specific material. Another factor is that conventional ball mills occupy an undue amount of space considering the output in terms of fineness and quantity from such mills. Conventional ball mills can also be considered inefiicient in that economically it is advantageous to employ such mills so that the grinding achieved in them is related to the size of the mill.

An object of the present invention is to provide new and improved ball mills. A related object of the present in vention is to provide ball mills which overcome many of the disadvantages and limitations of prior related structures such as are briefly described in the preceding. A closely related object of the present invention is to provide ball mills which are more efficient than prior structures in a number of different manners.

These and various other objects and advantages of the present invention will be more fully apparent from a detailed consideration of the remainder of this specification including the appended claims and the accompanying drawings in which:

FIG. 1 is a partially cross-sectioned view of one embodiment of a complete ball mill of the present invention;

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is a cross-sectional view taken along line 33 of FIG. 1;

FIG. 4 is a cross-sectional view taken along line 4--4 of FIG. 1;

FIG. 5 is a reduced diagrammatical showing of another embodiment of the ball mill of this invention;

FIG. 6 is a partially cross-sectioned view of still another embodiment of a complete ball mill of the present invention;

FIG. 7 is a cross-sectional view taken along line 77 of FIG. 6;

FIG. 8 is a cross-sectional view taken along line 88 of FIG. 6; and

FIG. 9 is a partial cross-section of another embodiment.

The accompanying drawings are primarily intended so as to clearly illustrate for explanatory purposes presently preferred embodiments of this invention. From a careful consideration of these drawings and of this specification those skilled in the grinding field will realize that a number of changes may be made in the precise ball mills illustrated through the use or exercise of routine engineering skill or ability without departing from the inventive features embodied in the ball mills shown in the drawings and described in this specification. Such features are considered to be defined and summarized by the appended claims.

However, as an aid toward understanding this invention it can be stated in essentially summary form that it concerns ball mills featuring constructions that include first and second shells so arranged that the first shell is disposed within the second shell and both shells are disposed on substantially the same axis of rotation. In one embodiment of a ball mill of this invention comprises a pair of such concentrically mounted shell wherein means are provided for rotating these shells independently of one another and preferably in opposite directions of rotation. In this embodiment means are also provided to introduce grinding balls or pebbles along with raw material to be ground into the outer of these shells and then for introducing material ground within the outer shell into the interior of the inner shell which is supplied separately with grinding balls, and thence from the interior of the inner shell out of the mill. In a second embodiment of the present invention two separate shells are concentrically arranged for relative rotation with respect to each other with an outer shell containing an inner shell. Means are provided whereby these shells may be rotated in the same or opposite directions independently of each other and whereby raw material and grinding balls or pebbles can be separately introduced into each of the shells and the ground material of each shell can be separately discharged so that the two shells operation as separate but cooperatively related ball mills.

The actual details of this invention will be more fully apparent in considering the accompanying drawings. Here there is shown in FIG. 1 a ball mill 10 comprising one form of this invention which includes a foundation 12 supporting a pair of end bearing support pedestals 14 and four pairs of intermediate bearing support pedestals 16. The intermediate pairs of hearing supports 16 each are provided with conventional split bearing caps 18 which house sleeve bearings that rotatively support the axles 20 of guide and support rollers 22. These rollers 22 are disposed in aligned confronting pairs in a manner shown in FIGS. 1 and 2 to enable them to rotatively support an outer cylindrical shell 24 of the ball mill on the circumferential tracks 26 disposed on the outer periphery of the outer shell 24. These roller assemblies comprise idlers and serve to support the outer shell rotatively as it is rotatably driven by a conventionally powered pinion 28 suitably supported on a shaft 30 in cooperation with a girt gear 32 fixedly attached in a suitable manner on 3- the outer periphery of the shell 24. The: end bearing support pedestals 14 are utilized tosupport theupper and lower bearing shells 34 and 36 which in turn rotatively support by means of'sleeve bearings 38 aligned tubular I shafts 40 and 42. The confronting ends of the hollow tubular shafts40 and 42'are secured byflanges 44'and 46 to the end closure plates 48 and 50 of inner hollow shell 52 further defined by the cylindrical wall 54. Preferably the shells 24 and 52 are located so as to have a common axis and the tubular shafts 40 andf42 are located so as to also extend along this axis from the extremities of'the inner shell 52. In order tocause'the.

inner shell to rotate the shaft 42 may be provided with a girt gear 56wl1ich cooperates with a drive pinion in i this stage will be of rathercoarse grade;

vided with a larger central opening 66 which is spaced from the tubular shaft 40 a sufiicient distance so as to allow passage of a conveyor tube68 past the tubular shaft 40 to the interior of the outer shell, 24. This conveyor tube is utilized to charge the interior of the outer shell with material 70 to be pulverized and a supply of I grinding balls 72. Such material and grinding balls may be supplied to the conveyor tube in any number of conventional manners such as by means of an attached hopper which is in turn supplied from a belt type conveyor. prevent passage of finely ground material to the sleeve bearing 64 a closely spaced annular cover 74 is attached to the flange 46 on the end plate 50 of the inner shell 52 and disposed to extend over the. inwardly turned flange 65 on the end wall 58 of the outer shell 24. This outer shell 24 is further defined by a plurality of radially disposed lifter vanes 76, as shown more clearly in FIG..

4, that are evenly spaced perpendicularly inwardly from the end plate 58. The lifter vanes 76 extend between the outer cylindrical wall 78 of the shell 24 to an annular conically shaped barrier 80 integrally attached to both the vanes 76 and the end plate 58.. A scoop feeder rotatingwith the inner mill could be substituted for, the lifter vanes 76. The liftervanes 76 are covered by a screen plate 82 which is annular in shape and is secured at itsv outer edge to the wall 78 and closely clears the cylindrical wall 54 of the shell 52 at its inner edge. T o withstand the abuse inflicted by the tumbling balls 72 and material 70 the interior of the cylindrical wall 78 is lined with a durable abrasive resistant wearplate or liner 84.

The inner shell 52 further comprises a dividing screen plate 86- located adjacent the end plate 48. Lifter vanes 88 similar to, the lifter vanes 76 are radiallydisposed in the space between the end plate 48 and dividing screen plate 86 and secured thereto as shown in FIG. 3. The spaces 90 between the lifter vanes 88 communicate through openings 92 in the end of the tubular shaft 40- V to a screw flight 24 fixedly secured within the tubular shaft 40.

96 is' preferably located completely around its exterior. A further liner 98 of the same character is preferably located with the interior of the inner shell 52. liners 96and 98 as well as the liner 84 may be secured so that there is no danger of the means holding these liners in place becoming inoperative during the operation of the complete ball mill 10."

grinding balls 72 or media of different sizes are located within the interior of each of the shells 24 and 52. Also during the operation of this ball mill 10 material to be These In order to prevent damage to the exterior 6 of the inner shell 52 another abrasive resistant wear liner' ground issupplied along with replacement grinding balls through the supply or feed conveyor tube 68 to the interior of the outer shell 24 as shown by the arrow 100. As the two shells 24 and 52 are simultaneously rotated the charge of material in the outer shell 24 will'become crushed and abraded to fine enough consistency to pass through the mesh of the screen plate 82 as indicated by the arrows 162 where the rotation of the lifter vanes 76 will pick up the finely divided material and cause it to fall'by gravity at the top of the cycle-against the end plate 50 of the inner shell 52 and passin the direction of'the arrow 104through mesh holes provided in the plate 50 to'th e interior of the inner shell52. The material at When within the inner shell 52 the material will be further pulverized by the crushing and grinding action of the grinding balls contained therein to a much finer grade. As the material becomes sufiiciently pulverized it will pass through the mesh of the divider screen 86 in thedirection of arrow ltldand be picked up by the rotating lifter vanes 88. b As the vanes-88 rotatepast the top of their cycle the finely divided material will fall by gravity as indicated by the arrow'1ti8 onto the screw flight which is attached to and rotating with the tubular shaft 40. The action' of the screw flight 9 4-will convey the finely divided material through the tubular shaft 40 in the direction of the arrow 110. The tubular shaft 40 may be directed toanother treatment stage either directly or by means of a conventional conveyor not shown.

In utilizing the ball mill 19 in the manner described relatively coarse grinding is, accomplished'in the area between the inner and outer shells 52 and 24, respectively, and fin'er grinding is accomplished within the inner shell 52. Y Because of this. in order to promote grinding efficiency it is considered preferable to utilize larger particles for grinding operations or-as a-grinding media in the outer shell 24' than in the inner shell 52.. Also the openings in the screen 82 are preferably of larger dimension than the openings; provided in the divider screen 86 within the innor shell 24. It is to be pointed out that the supply of grinding balls or media within the inner shell 24 may be conventionally supplied through the interior. of the tubular shaft 42 as indicated by the arrow 112. "Normally; in the operation of this ballv mill, there is'no significant problem in the structure shown of particles of grinding media becoming lodged between close fitting relatively moving parts; such as between'the screen 82 and liners 96 and 84. because the rotation of'the mill will tend'to throw out any particleswhich will tend to become so lodged. Also the s'pacin'gbetween adjacent parts is preferably significantly greater than the larger dimensions of any particles of materials pulverized so as to negate any reasonable danger. of the material or grinding media becoming jammed therebetween in such a manner as to impede the normal rotation of the shells 24 and 52.

g In order to facilitate the flow of material through the ball mill, if desired the axis of the two shells can be canted in the direction of desired flow to a slight degree. Such an arrangement is shown diagrammatically in the embodiment of this invention shown in FIG. 5. If such canting is effected, it will of course, be necessary to cut the angles of the support rollers 22 to maintain the desired position of the ball mill with respect to theseroller supports. As shown in FIG. 5, the ball mill 118 is, diagrammatically shown with the axis 120 of the outer shell 122 canted downwardly to the right and the direction of the axis 124" of the inner shell 126, canted downwardly to the left. It is to be understoodthat otherwise the construction of the embodiment of the ball mill,118 is the same as the ball mill .10 and the operation of each ball mill 10 and 118 is the same as described in conjunction with the ball mill 10. i

l FIGS.- 6-8 show. still another embodiment of a ball mill 20f! falling within the scope, of the present invention.

The ball mill 200 differs from the ball mills 10 and 118,

previously described, in that it comprises two separate ball mills that are independently supplied with charges of raw material to be ground and supplies of grinding balls or pebbles. This embodiment comprises the same support arrangement including the members 14 and drive gear 56 for the inner shell member 202, and the same drive gear 28 and supporting rollers and guide tracks 26 are utilized to support and drive the outer shell 204. Also, the same bearing shells 34 are utilized to support the tubular shafts 40 and 42 of the inner shell 202. Essentially, the inner shell 202 differs from the shell 52 of the ball mill in that it is provided With a solid entrance end plate 206 which is provided with a central opening communicating with the entrance tubular shaft 42 that is utilized to supply both raw material to be ground and grinding balls to the interior of the inner shell 202 in the manner previously described in conjunction with the ball mill 10. Otherwise, the inner shell 202 is of the same construction as that of ball mill 10 as represented by the common reference characters shown in FIG. 6.

The outer shell of the ball mill 200 is similar to the outer shell 24 of the ball mill 10 shown in FIGS. 1-4 as represented by the common reference characters. However, the outer shell 204 includes a scoop feed assembly 208 and a separate discharge assembly 210. The scoop feed assembly 208 comprises a truncated conical extension 212 on a solid end wall 214 which includes a rotatable connection 216 with the tubular shaft 42 of the inner shell 202. This scoop feed assembly includes a tubular scoop extension 218 having an open end 220 disposed in a raw material and grinding ball housing 222 which is supplied With raw material and grinding balls through an input conduit 224. The housing 222 is suitably supported in a fixed position on a support beam 226. With this arrangement raw material and grinding balls or pebbles entering the housing 222 through the input conduit 224 are scooped up by the scoop 218 as the outer shell is rotated whereby they are led by the conical shape of the extension 212 to the interior of the outer shell 204.

The discharge assembly 210 of the outer shell 204 comprises an interior end screen 230 and lifters 232 similar to those utilized in the outer shell 24 of the ball mill 10 and a conical discharge extension 234 which communicates with a stationary collector housing 236 that is provided with a discharge conduit 238.

By virtue of the above arrangement, the ball mill 200 can be utilized to grind separate raw materials in the two shells 202 and 204 or the material discharged from the larger mill shell 204 can be led from the discharge conduit 238 to the input conduit 42 of the smaller mill shell 202 for further reduction in particle size.

It has been found that when the inner and outer shells of the ball mills 10, 118 and 200 are driven in reverse rotary directions that an unexpected advantage is realized in that the grinding balls or pebbles of the outer shells of these mills are randomly scattered along with the material being ground in such a manner as to vastly improve the grinding efficiency of the outer shells. However, if desired the inner and outer shells of these ball mills may be rotated in the same direction.

Another embodiment is shown in FIGURE 9 where the ball mill 300 has an outer shell 302 rotatably mounted on support rollers 22 and driven by ring gear 32 as is described hereinbefore. Contained within the outer shell 302 is an inner shell 304 which is supported on shafts 306 and 308 which in turn are supported in the pedestal bearings 34. Shaft 306 carries the drive gear 56 for rotation of the inner shell 304. The inner shell 304 is supported on the shafts 306 and 303 by means of spiders 310 and 312 so that material may enter through spider 312 from loading chute 314 and may pass out through spider 310 after passing screen 316. The inner shell 304 is provided with wear resistant lining and covering 318 and 320, respectively.

After the material is preliminarily ground in the inner mill 304 by being rotated with grinding balls or the like,

it passes through screen 316, spider 310, and is gravity discharged into the inside of outer shell 302. Outer shell 302 is provided with a wear resistant lining 322. After the material is ground even more finely within the outer shell 302, it is discharged through a screen 324. After discharge it may be picked up by lifting vanes, or scoop means and discharged into an outlet conveyor as is hereinbefore disclosed.

From the foregoing it is apparent that new ball mill devices have been provided which by virtue of the fiow of material to be ground into the outer shells and thence to the inner shells, in the case of the ball mills 10 and 118 and if desired in the ball mill 200, so as to effect a much higher efficiency than other types of unitary ball mill constructions. It is also to be realized that the ball mills disclosed above also effect higher operating efficiencies when the inner and outer shells are rotated in opposite directions of rotation.

It will be realized by those skilled in the art to which this invention pertains that by ordinary skills a variety of differently appearing ball mill constructions may be designed and constructed utilizing the features of the invention as embodied in the above described example of the device of this invention. Accordingly, since the structures of this invention are susceptible to such modification the invention is to be considered as being limited only by the appended claims.

I claim:

1. A ball mill which includes:

first and second ball mill shells having different diameters, each of said shells having an axis, said shells being located concentrically about the same axis, the interior of the larger of said shells being spaced from the exterior of the other of said shells;

means for turning said shells independently of one another;

means for introducing material to be ground into the outer of said shells;

means for introducing ground material from the outer of said shells into the inner of said shells; and means for removing the ground material from the inner of said shells.

2. A ball mill as defined in claim 1 wherein:

the axis of the said first ball mill shell and the axis of said second ball mill shell are canted in opposite directions to facilitate the flow of material through said shells.

3. A ball mill as defined in claim 1 wherein:

said means for turning said shells functions to turn said shells in the same direction of rotation.

4. A ball mill as defined in claim 1 wherein:

said means for turning said shells functions to turn said shells in opposite directions of rotation.

5. A ball mill as defined in claim 1 wherein:

said means for turning said shells functions to turn said shells at the same angular velocity.

6. A ball mill as defined in claim 1 wherein:

said means for turning said shells functions to turn said shells at different angular velocities.

7. A ball mill as defined in claim 6 wherein:

the smaller of said shells is turned by said means for turning said shells at a faster angular velocity than the angular velocity of said larger of said shells.

8. A ball mill which includes:

first and second cylinders having different diameters,

said cylinders being concentrically located about the same axis;

means for turning said cylinders independently of one another;

means for introducing material to be ground into the outer of said cylinders;

means for introducing ground material from the outer of said cylinders into the inner of said cylinders; and means for removing ground material from the inner of said cylinders.

7 9. A ball mill as defined in'claim 8 whereinz the axes of said first and-second cylindersare canted a first cylindrical millrotatably mounted about a horizontal axis on. said rotable support means; bearingmeans;

a second cylindrical mill rotatably mounted about said 7 horizontal axis on said bearing means, said second cylindrical mill being ofsmallerdiameter than said first cylindrical mill and being located within the interior of said first cylindrical mill;

meansufor introducing material to beground into the interior of said first cylindrical mill;

means for conveying groundmaterial from the interior of said first cylindrical mill into the interior of said second cylindrical mill;

means for conveying ground material from thesinterior other means for rotating said second cylindrical mill about its axis, independently of said; first means within the interior of said first cylindrical mills 11. A; ball mill which=includesr first and second ballmill shells having different diameters, each: of said shells having an axis; said shells being 7, located concentrically about the same axis with the first shell located within the second shell and wherein; the exterior of'the first shell is spaced from the innerwall of the secondishell;

means for rotating said shells independently of one another;

separate meansfor introducing raw material to be ground and grinding media separately. into each of said shells; and

separate discharge means for separately discharging ground raw material from each of Said shells.

12'; A ball mill asdefinedin claim' 11 wherein:

said means forgrotating said shells independently of one another operates to rotate said shells, inqopposite directionsof rotation.

13. A ball mill as'defined" in claim 11" wherein:

said means for rotating said shells independently of one another operates to rotate said shells in the same direction of rotation.

1,520,537 DIe Markus Dec. 23, 1924 7 1,710,659 Griesen Apr. 23', 1929 

1. A BALL MILL WHICH INCLUDES: FIRST AND SECOND BALL MILL SHELLS HAVING DIFFERENT DIAMETERS, EACH OF SAID SHELLS HAVING AN AXIS, SAID SHELLS BEING LOCATED CONCENTRICALLY ABOUT THE SAME AXIS, THE INTERIOR OF THE LARGER OF SAID SHELLS BEING SPACED FROM THE EXTERIOR OF THE OTHER OF SAID SHELLS; MEANS FOR TURNING SAID SHELLS INDEPENDENTLY OF ONE ANOTHER; MEANS FOR INTRODUCING MATERIAL TO BE GROUND INTO THE OUTER OF SAID SHELLS; MEANS FOR INTRODUCING GROUND MATERIAL FROM THE OUTER OF SAID SHELLS INTO THE INNER OF SAID SHELLS; MEANS FOR REMOVING THE GROUND MATERIAL FROM THE INNER OF SAID SHELLS. 